Hello,
I was using this:
#appMenu-fxa-separator { border-image: unset ; }
to make the separator between account and the rest of the menu (circled in red) look consistent with the other separators, but after the update it stopped working.
I thought that the ID may have been changed so I checked, but ID is still use so I don’t know how to fix it :/
Also what happened to the separator between find page and translate (circled in green)? It’s the only one what is longer than the rest, would there be a way to make it look consistent with the rest as well?

Damn, I’m an idiot - I looked for the wrong thing in the source. But yes, apparently the quit-button isn’t there on macOS, for whatever reason.